In order to determine the quality of the catalytic converter for installation in a motor vehicle and the quality of an installed catalytic converter, it is conventional to measure the oxygen storage capacity of the catalytic converter. In the process, measurements are taken such that the delay time between the oxygen probe signal of a probe upstream and an oxygen probe signal of an oxygen probe downstream from the catalytic converter is measured. This delay time corresponds to the oxygen storage capacity of the catalytic converter.
It is, however, problematical that the probe signal upstream and downstream from the catalytic converter changes not only as a function of the storage of oxygen, but, moreover, is influenced by the dynamic properties of the oxygen probe used downstream from the catalytic converter and by the different dynamics of the two probes used. The measured delay time therefore corresponds to the sum of the time delay which is actually to be measured based on the oxygen storage capacity of the catalytic converter and the probe delay time dictated by the probe dynamics.
This results in that for the case of a slow oxygen probe, overly large delay times are measured and thus an overly large oxygen storage capacity of the catalytic converter is deduced. The catalytic converter is therefore evaluated as too good compared to its actual efficiency.
In particular, for a comparatively slow oxygen probe and low oxygen storage capacity of the catalytic converter, the case may arise that solely based on the properties of the oxygen probe used a bad catalytic converter is assessed as good, that is, a misdiagnosis occurs.
For this reason there are currently plans, mainly in the USA, to legally prevent faulty assessments.
But the problem is that using the rising or falling edge of the signal of a jump probe, which is used as the oxygen probe, for a rich or lean transition it is possible only with great difficulty to factor in a probe-dictated delay time.
Thus the object of the invention is to devise a process which is improved in this respect.